All notices, requestsand other communications to any party hereunder shall beinwriting and either deliveredpersonally, telecopied or sent by certifiedorregistered mail, postage prepaid.
Section 6532(a)(1) indicates that the mailing of the Notice of Claim Disallowance by certifiedorregisteredmail triggers the beginning of the two-year limitations period in which the taxpayer can bring a suit for refund.